Re: [Xen-devel] [PATCH 0/2] Improve hpet accuracy

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 9/6/08 00:26, "Dave Winchell" <dwinchell@xxxxxxxxxxxxxxx> wrote:

> > 4) config file parameters
>
> Hpet enabled. Timer_mode set to HVM_HPET_guest_computes_missed_ticks
> for all Linux guests and to HVM_HPET_guest_does_not_compute_missed_ticks
> for Windows 2k8-64 and Vista 64.
> 8 vcpus for Linux and 2 for Windows.

These new HVM_HPET options seems a weird design choice. It appears that you can only set these or one of the old options, so there’s not actually any independence between the mode used by vpt.c and the mode used by hpet.c. At guest install time you ought to be able to tell whether the guest will use hpet or not based on its version (RHELx, SLESy, Winz etc etc) and decide whether missed-ticks accounting is required or not.

I’d be more agreeable to a partch that stripped out the physical hpet accesses (since you say they are not the reason for the improvement in accuracy), built hpet on top of vpt, and added the necessary extra mechanisms to deal with interrupt broadcasts into vpt.c. And which was split into more separate pieces of mechanism.

 -- Keir



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